If you start to worry about how possible a solution is while you're coming up with ideas, you slow down your ability to come up with ideas in the first place. Even if the technology to create your idea doesn't exist yet, it doesn't matter: Write it down.
Maybe aspects of that idea will be possible, and will lead to the solution you eventually choose. Maybe a different version of the same solution will be completely possible. Maybe a developer will see your "impossible" idea and tell you that actually, it's very possible with a couple of tweaks.
A fundamental truth of ideation is that ideas lead to other ideas, and stopping to consider whether a solution is possible gets in the way of that process. Once you've come up with a long list of ideas, then you can start to consider which of them are possible.Judgement free → ← Functional fixedness is a problem Back to the table of contents